Process of making hydrogen fluorid.



"3: a mor use w th i CLIS CO'MPANY, Q WILMING-TGN, DELAWARE, A CORFORATIO'D? 9F EBIJCESS fil MAKING HYBROGEN JELUGRID.

To all whom it may voncern:

Be it known that I. ROBERT M. Cerium a citizen of the United States, residing at Franklin, county of Sussex and State of New Jersey have invented certain new and useful improvements in Processes of Making Hydrogen Fluorid, fully described and represented in the following specification.

The present inventionrelates to an in1- proved process for the recovery of hydrofluoric acid from solutions of hydrofluosilicic acid and other fluosilicates.

In my Patent 1,219,438, patented March.

20, 1. 917 I have described a method of making decolorizing material which consists in acting upon certain starting materials containing silica, with hydrofluoric acid. In that case the solids are washed and constilute the desired product. The filtrate is a solution containing fluoriu in combination. The recovery of the fiuorin us hydrofluoric. acid is advantageous for the economical carrying out of the process. (line method of recovering the hydrofluoric acid described in that "patent comprises the addition of aluminum. oxid (A1 0 in sullicient quantitiec to precipitate silica. (SiO decanting the supernatant liquid heating it under pressure to crystallize the aluiniuum liuorid (Alla) separating the crystalline mass, and then heating it to drive oil the hydrofluoric acid as a gas, which is absorbed by suitable contact with water.

I have now discovered that by the use of oxid of iron and particularly the ferric oxid l e fi a better and more reliable result is obtained and a simplification of the operations becomes possible.

lfn carrying out the new process a solution containing the tluosilicates or liydrofiuosilicic acid. or both is treated with o-xi-d of iron and particularly the ferric one. as for example, in comininuted form in sufiicient quantity to combine with all the fluorin present in the solution. ferric oxid may safely be used and is pos v ihle on account of the low cost of the ferric oxide "his results in the precipitation of silha (Siih) and the formation of an iron lluorid probably Fo which re: iains in the solu ion, Agitation of the solution will exiei'litethe reaction.

'l he solution should be'hoated and most Specification of Letters Eatent.

An oi the Patented Feb. Elli Mi li npgliestion filed June 9, 1917. Serial No. 173,685.

SiO and other impurities. The filtrate may then be evaporated in any usual way until ass the iron fluorid crystallizes out, or the liltrate may be heated in a closed vessel under pressure, which results in the formation of crystals of iron liuorid. The crystalline product is then separated from the mother liquor.

The solids thus obtained are then subjected to heat treatment in the presence of steam whereby the compound is broken up to set free the fluorin as hydrofluoric acid. Treatment with superheated steam will accomplish the desired result. The residue is iron'oxid.

"While .l: have mentioned the use of ferric oxid (R50 it is to be understood that this includes eitier the henmtite, or hydrated ferric oxid such as 2(Fe O ).H O.

The gaseous HF driven ofi may be absorbed in water to give the desired solution oi hydrofluoric acid. l t is very advantageous to use the mother liquor above men. tioned for this absorption. Any suitable absorption apparatus may be employed for this urpose, such as the usual wash tower.

The reactions which occur may he represented generally as follows orin may vary, it being; known that this is possible, as shown by the variations in vapor (lei'isity of hydrogen fiuorid shove and below about 89 (3. The equations stated, however, ere, suflicicut for practical purposes in determining approximately the relative amount of Fe O to be added to any given solution containing the elements Si and F.

What I claim is:

1. The process of reeovering fluorin'as hydrogen fluorid from solutions containing it in combination with silicon, which consists in adding to such solution an oxid of iron, removing the precipitate, crystallizing the iron fiuoridfrom the filtrate, then subjecting the iron fiuorid thus obtained to the action of heat and steam, and absorbing with Water the hydrogen flnorid thus driven ofi. I

2. The process of recovering fluorin as hydrogen fiuorid from solutions containing it in combination with silicon, which consists in adding to such solution F e 0 removing the precipitate,subjecting the filtrate to mes es heat whereby the iron fiuorid is crystallized, separating the. crystalline mass from the mother liquor, subjecting it to the action.

of steam and heat to drive ofi the HF and absorbing the latter with water.

3. The process of recovering fluorin as hydrogen fluorid from solutions containing it in combination with silicon, which consists in adding to such solution an end 01? iron,

removing the precipitate, crystallizing the ROBERT M. CATLIN. 

